Valve Adjustment

[pschuyler]

I just received my new BMW Owners manual for my R75.

The valve adjustment measurements state .15 and .20 for intake/exhaust, which differs from Clymers. I'm assuming the BMW manual is correct, any input from the forum?

[lkchris]

Yeah, the information in the BMW manual came from BMW.

As for Clymers, who knows?

[20774]

I'll guess that your Clymers says 0.10/0.15. The value settings have changed, even from BMW, over the years. The lastest service bulletin that I can find (ca 1984) set the clearances to 0.10/0.20 intake/exhaust after break-in. But the 0.15 for intake is a good thing to do. It doesn't detract noticeably from engine performance but does allow the valve to rest on the seat for a fraction of time longer, helping with heat transfer. The intake valve needs this less than the exhaust valve due to the in-rush of cooling air-gas mixture.

[DennisDarrow]

Not that I quote Paul Glaves as the end all of information; but he discusses valves in depth in the July issue of "The News". He is much more in touch with bulletins, etc than I will ever be..........on page 30, "The latest bulletin calls for all Airheads to be set at 0.15 intake and 0.20 exhaust".


Thanks Paul........Dennis

[pschuyler]

Thanks that article was right under my nose the whole time.

[Manfred]

FWIW, Snowbum's airhead top end manual says to set intake at 0.006 in and exhaust to 0.010 in.

[20774]

FWIW, Snowbum's airhead top end manual says to set intake at 0.006 in and exhaust to 0.010 in.

That would be Oak's topend manual. The 0.010 seems a bit much and will result in a bit more noise. Probably OK but 0.008 works just fine. FWIW, Snowbum has discussed using 0.0085 for the exhaust. I think he does it like others have mentioned...0.009 won't go but 0.008 will slip through.

[rbleau]

Howdy Pete !

Looks like you need to set em where you like !

:lurk

[ebeeby]

Heck, I've always used .006 and .008 as I thought that was "correct" for an R75/5. Come to think of it, I can't recall where I got those specs.
Old age sucks.

[Radar41]

Heck, I've always used .006 and .008 as I thought that was "correct" for an R75/5. Come to think of it, I can't recall where I got those specs.
Old age sucks.

According to my master tech. (he was a BMW mech in those days) .006 intake and .008 exhaust is correct for my 84 R100RS don't know about the others. :bolt

[jamesdunn]

Not that I quote Paul Glaves as the end all of information; but he discusses valves in depth in the July issue of "The News". He is much more in touch with bulletins, etc than I will ever be..........on page 30, "The latest bulletin calls for all Airheads to be set at 0.15 intake and 0.20 exhaust".


Thanks Paul........Dennis

Matt Parkhouse, "Keep 'em Flying", recently recommended this setting as I recall, not Paul Glaves. BMW recommends 0.10 mm for intake and 0.20 mm for exhaust, but as pointed out in post #3 by 20774 there are benefits to a "looser" intake setting. I use 0.15 mm intake and 0.20 mm exhaust ; a little more noise perhaps but I love the sound.

[DennisDarrow]

whoa......I am ever bad......MATT......sorry for getting the credit wrong.............one of those old ages moments I guess........But at least I was so impressed with the information from YOU that I remembered that..........God bless the old guys......Dennis

[GeorgeRyals]

Cams are ground with acceleration and deceleration ramps on the lobes. The purpose of these ramps is to start lifting the lifter and valve gear slowly to overcome the inertia of the valve and valve gear as it begins to move and lift the valve off the seat. Then the lobe basically whacks the valve nearly to full lift and there is a ramp slowing the rate of lift as the valve reaches full open. This is to keep the valve gear from floating away from the cam and overlifting the valve, maybe tagging the piston. As the lobe begins to rotate out from under the lifter there is a ramp that starts the lifter slowly down, once it is moving the lobe drops off real fast and almost closes the valve. Now here it the point of this long winded post. The lifter gets to the deceleration ramp that slows the rate of drop (valve closing) and gently sets the valve down on the seat. If you arbitrarialy increase the valve clearance adjustment beyond what the engine/cam designers intended, the valve slams into the seat before the deceleration ramp is finished doing its job. This pounds the seat and valve and causes the adjustment to close up a lot faster than normal seat/valve wear. Going from .10 mm to .15 mm doesn'r seem like much, but it is a 50% increase in valve clearence.

[jamesdunn]

Quote from George R.:If you arbitrarialy increase the valve clearance adjustment beyond what the engine/cam designers intended, the valve slams into the seat before the deceleration ramp is finished doing its job. This pounds the seat and valve and causes the adjustment to close up a lot faster than normal seat/valve wear. Going from .10 mm to .15 mm doesn'r seem like much, but it is a 50% increase in valve clearence. ; unquote.

Great post George and informative. But if so many "gurus" recommend the .15 vs. .10 have they not considered any ill effects? I have been using the .15 on intakes and detect no negative consequences as yet. Matt Parkhouse does say in the July "Keep 'em Flying" ,and I paraphrase, " You can use a tighter setting than the .15 intake if you so choose.", referring to the .10 gap, I suppose.

Your thoughts pleas, as I really resp[ect Matt's opinions and advice.

[keelerb]

An interesting debate. I use the .006/.008 clearances myself (saves memory, among other things, as my Commando uses the same settings), thinking that looser is better (more time to cool on the seat), although maybe not so important for the intake valves. I have an 84, so want to fend off the inevitable rebuild as long as I can.

Will be interested in everyone's views/experiences.

[carockwell]

No question about it, if your valve clearances are too small, you can burn a valve prematurely, but this takes time. If you set your clearance too large, your valves get hammered bouncing off the seats and the valves can break in less than 10 miles. The moral of the story is that either too little or too much clearance is bad. Too much clearance can go bad really quickly. It is not that .15 is too much for the intake valve, but don't run off a think that .25 must be even better. I saw a lot of people make that mistake when building modified car engines. Oak suggests that the clearances be opened a little extra for the first 50 miles to give the valve seats a little room to bed into the heads (.20mm intake and .25mm exhaust), which I am sure is a reasonable idea. Then he suggest running at .15 intake and .20 exhaust for the rest of the engine life. This seems reasonable based on my VW Beetle and Porsche experience too.

[jamesdunn]

No question about it, if your valve clearances are too small, you can burn a valve prematurely, but this takes time. If you set your clearance too large, your valves get hammered bouncing off the seats and the valves can break in less than 10 miles. The moral of the story is that either too little or too much clearance is bad. Too much clearance can go bad really quickly. It is not that .15 is too much for the intake valve, but don't run off a think that .25 must be even better. I saw a lot of people make that mistake when building modified car engines. Oak suggests that the clearances be opened a little extra for the first 50 miles to give the valve seats a little room to bed into the heads (.20mm intake and .25mm exhaust), which I am sure is a reasonable idea. Then he suggest running at .15 intake and .20 exhaust for the rest of the engine life. This seems reasonable based on my VW Beetle and Porsche experience too.

Great post and one that makes a lot of sense. Thanks. I will continue to set at .15mm intake and .20mm exhaust. As mentioned by George Ryals "going from .10mm to .15mm is a 50% increase. As such, it seems .15mm intake, is the limit for a "loose" setting.

[GeorgeRyals]

jamesdunn, I too have the utmost respect for Matt and the other airhead mechanics who have shared their years of experience and knowledge with the rest of us who maintain our airheads as a hobby.
Even though intuition says that having a valve on the seat longer is good for transfering heat, my intuition is not enough to make me believe the engineers that designed these engines got it a little wrong. The way I look at it, is if the valve needed to be on the seat a little longer the engineers would have discovered this during the months of dyno runs they must have done before releasing the design for manufacture. One other thing to think about on this theory of more time on the seat to cool the valve being good or necessary, if the valve needs more seat time, "why would BMW manufacture long duration cams for these engines?" They hold the valves off the seats a lot longer than the cams most of us are running.

Why sacrifice a little valve lift and duration if you don't REALLY have too?

[shire2000]

I have been using the 006/.008 clearances for all my airheads over the past 20 odd years. Have found no ill effects. Not found it has made any difference as to when the inevitable valve job needs doing. And when they need doing, I just take the heads off and have them done. Part of owning an Airhead, or any engine for that matter. They all need a valve job eventually.

[ebeeby]

I have been using the 006/.008 clearances for all my airheads over the past 20 odd years. Have found no ill effects. Not found it has made any difference as to when the inevitable valve job needs doing. And when they need doing, I just take the heads off and have them done. Part of owning an Airhead, or any engine for that matter. They all need a valve job eventually.

As I said earlier, I'm a .006 and .008 guy (though I can't recall why, old age, yada yada)
That said, I really don't understand where this .10 and .15 is coming from. This is news to me. I have NEVER hear those used until I read this thread. So is there some sort of metric/thousandths disconnect going on here?
Inquiring minds want to know....

[carockwell]

Yes, its a metric deal. .10 mm is ,004 thousandths of an inch and .15 is .006 inch.

As for the gent who was talking about all the hundreds (thousands?) of dyno runs performed by the elves in the BMW Black Forest, this is certainly not what happened. BMW engineers probably ran two engines on a dyno to failure and fixed the first one or two things that went wrong. Then came a road trial or two for 50,000 kilometers and voila! Off to the beta testers..er....customers. The truth is factory engineers don't know much more than the few test results they get and the service history of prior models. Engineers are mostly concerned with the dimensions to get things to fit, and the tooling requirements necessary to get the product made. Talk to good German factory engineers and they have a LOT of respect for the knowledge of good mechanics. In fact the mechanics usually know more about the whole product and how all the systems work than the engineers.

[20774]

Hmmm...I would think that the experience gained since 1923 on all various forms of the boxer twin goes a long way to understanding how to "design" a '70s twin and what works best or not. Dyno runs? Sure. Road Tests? Most likely. But those may have been more for evaluating other issues like comfort, handling, developing specs for the manuals, etc. They probably had a good handle on what the basic engine was going to do and could tolerate. The valve clearances have migrated around a bit over the years. The fact that they did suggest different values, and that owners are using everything between 0.10 and 0.20, is probably a testament to the robustness of the engine design and that it probably doesn't really make any difference. It may or may not change the time/mileage at which the upper end needs to be redone. It's probably lost in the statistical variation of all the other parameters that go with owing and riding an Airhead...type of oil used, change intervals, type of riding, weather, quality of filters used, etc. My 0.02...

[sumran]

It's probably lost in the statistical variation of all the other parameters that go with owing and riding an Airhead...type of oil used, change intervals, type of riding, weather, quality of filters used, etc. My 0.02...

+1. They are not all the same.

I run mine at .10 mm and .20 mm. I change the oil every 2,500 miles and change the oil filter every other oil change. I check the valves every 5,000 miles at the same time I change the filter. I keep a log of which valves need adjusting and how much. In the last 10k the intakes have been checked but did not need adjustment. Exhaust valves needed about .01 mm at 10K.

If I was getting more movement on the intakes, I would run them at the larger clearance. Since the valves are very stable, .10 mm works well and should improve the wear characteristics and run a little quieter.

[Rod Sheridan]

As I said earlier, I'm a .006 and .008 guy (though I can't recall why, old age, yada yada)
That said, I really don't understand where this .10 and .15 is coming from. This is news to me. I have NEVER hear those used until I read this thread. So is there some sort of metric/thousandths disconnect going on here?
Inquiring minds want to know....

Not Metric/thousands however it is mm/inch conversion.

If you multiply 0.006 inches X 25.4mm/inch you'll arrive at about 0.15mm.

0.008" converts to about 0.20mm.

On my airheads I use 0.10mm and 0.20mm.......Regards, Rod.

[jamesdunn]

As I said earlier, I'm a .006 and .008 guy (though I can't recall why, old age, yada yada)
That said, I really don't understand where this .10 and .15 is coming from. This is news to me. I have NEVER hear those used until I read this thread. So is there some sort of metric/thousandths disconnect going on here?
Inquiring minds want to know....

It matters not if one uses mm or inches to set valves. I have used both. And as mentioned here elsewhere there are conversions. Some feeler gauge sets even show mm/inch measurements on each gauge. I think the thread started referring to mm. I use mm because I have some individual metric feeler gages that are small and easy to use, even when setting the points gap (Yes I still have points.)

.006 in. equals .15mm and .008 in. equals .20mm, so you're setting your intake valves at the "looser" setting.

[tghsmith]

the best way an airhead owner can spend 6-10 bucks is part #71119090154 a compact set of feeler guages that takes up less space than the average house key.. small tipped so you can get a nice feel and not twist messing up the settings. Included are 5,10,15, 20, for the valves(I most often bracket my settings, ie intake a loose 10 and a tight 15. two readings are better than one) also on this set are guages for the points gap and plug gap.. plus a strange little U-guage thats for setting the correct free-play in the cable of the under the tank master cylinder, thats why the little groove is made into the piston!!! ps the whole set is even marked, intake,breaker points ans so on (reading german req.)

[jamesdunn]

Not Metric/thousands however it is mm/inch conversion.

If you multiply 0.006 inches X 25.4mm/inch you'll arrive at about 0.15mm.

0.008" converts to about 0.20mm.

On my airheads I use 0.10mm and 0.20mm.......Regards, Rod.

Oops! Missed Rod's post! This is correct.

[barryg]

If your going to err, do so on the side of being a little loose.

[orbitangel]

Matt Parkhouse, "Keep 'em Flying", recently recommended this setting as I recall, not Paul Glaves. BMW recommends 0.10 mm for intake and 0.20 mm for exhaust, but as pointed out in post #3 by 20774 there are benefits to a "looser" intake setting. I use 0.15 mm intake and 0.20 mm exhaust ; a little more noise perhaps but I love the sound.

James!

Thank YOU!

Yours is the ELEVENTH post in this thread - all kinds of various NUMBERS have been thrown around for valve clearances.

Yours is the first post (and the ONLY one, so far) that mentions anything at all about UNITS!

In support of RBLEAU's position, it would appear that one selects one's favorite digits (e.g. .008 or 0.15 or whatever) and then selects any random unit of measure, feet, inches, miles, you name it!

Holy crap! No wonder nobody know how to set their valves!

[mmmalmberg]

I ran .006" and .008" on my /2, for 12 years with no problems. During that time BMW changed the recommendation to .004 and .008", and on my subsequent bikes I've always run those numbers except when breaking in newly done heads. In any case, it's always been the exhaust valves that get toasted, so for my money, I'm happy with .004"/.008" as long as I am staying on top of adjustments, which I do since it takes so little time to check...

Speaking of which, that /2, bless her soul, would run 25K miles and the valves would still be within about .0005" of where I set them. Unfrickinbelievable.

[amiles]

When I bought my 90/6 I was provided with an owners manual and tool kit. I have been using the feeler gauge so provided with a double check in the book for each valve adjustment. I can't remember E from A so I double check.


The owners manual says

Inlet metric .15 Inch 0.006

Exhaust metric .20 Inch 0.008


The feeler Gauge shows E Ventil Kalt 15 A Ventil Kalt 20

The gauge is a little worn and hard to read.

So far this has served me well.

[pmdave]

Waaaay back when, the valve clearance specs for my R100 were .004" for intake and .006" for exhaust. But then BMW went through a succession of attempts to cure exhaust valve problems. The intakes get lots of cooling from the fuel vapor, but the exhausts live in a much hotter environment.

So, after several attempts to solve the valve problems, BMW came out with recommendations for .006" and .008". The .008" clearance allows a bit more seat wear or valve stretching before the clearance is used up. Once the exhaust valves lose clearance, it's a matter of minutes before they burn the seats or heat up the valve head until it starts to "tulip."

I had lots of valve problems when pulling a sidecar at speed, and therefore a bit of experience with different solutions. IMHO, the latest valves/seats with the 30 degree seat angle seem to last much longer. And adjusting the exhausts to .008" seems to work just fine.

However, I set my intakes to .005, splitting the difference between the original .004" spec and the later .006" recommendation. The valves originally set to .004 were designed to work with the stock cams/followers/rockers. IMHO, they don't need .006" with the current configuration and use. But, if I were experiencing recession problems with my exhausts, I'd try increasing clearance to .009"

Remember, valve clearances don't stay constant, so they will have clearances other than what you set as the parts wear/heat/cool.

OK, you set yours the way you want to. What's really important is to set those valves whenever they start to get quiet. The symptom of tight exhausts is that the engine is REALLY quiet, and after a long hot run the engine stalls at idle. Rather than start twiddling with the carbs, shut it down, have dinner while it's cooling down, collect some real estate ad magazines (to soak up the oil that drizzles out of the valve covers) and set those babies.

pmdave

[RecycledRS]

Best reply yet Dave.

[orbitangel]

Best reply yet Dave.

I second that emotion. An excellent post indeed, Dave.

I am currently riding my third R100RS (a '77, after owning another '77, way back when followed by a '78.)

Like the bumble bee who does not know he's too heavy to fly, I never knew about any of the BMW Technical Service Bulletins, Service Letters or any other technical memoranda sent to dealers.
When I started doing this I didn't hang-out at BMW dealerships and there was no World Wide Web.

So I just did what the book said: .004 in. on the intakes, .006 in. on the exhausts.
Maybe it is nothing more than ignorant, blind luck but I have never had any valve problems, valve recession or any other engine "failures."

I should also mention that I had never put more than 80K miles on any given machine. (Just circumstances - I hope to ride this RS a half a million miles!)

I still use those settings today (although I may reconsider, after reading Dave's post.)

One final point. I check my valves pretty frequently, like at the beginning of every riding season, before and after any major trip and any other time I get the urge.
I have done this so many times it takes me about fifteen minutes if I'm not in a hurry. And I never rush this important task.

I use a GO/NO GO method where, for example, .004 in. fits easily (with a slight drag) and .005 in. feeler gauge won't go in. I use a quality (Snap-On) feeler gauge.

BTW, I also do a static ignition timing check every time I check valve lash. Is there any better time to do that?

This has become a labor of love on my beloved Airhead and I seldom see more than a half a thousandth drift from one check to the next.

If I find one out by half a thousandth, I adjust it. What the hell, I'm already in there!

Personally, I turn the crank (in the forward direction only) with an Allen socket in the alternator rotor bolt, 1/4 in. drive handle and sparkplugs OUT.

I would NEVER screw around with turning the rear wheel in gear. That's just me.

If I were more methodical and better organized I'd keep a little notebook, a logbook where I'd track my valve clearances by date, mileage, whether I simply did a check (no adjustment required) or a check & adjustment.

I think the biggest point is not to IGNORE the valve clearances (this also applies to oil and filter changes, the drive splines, wheel bearings, head bearings, carbs, brakes and so on.)

Thanks, Dave! :dance

[pmdave]

I've drilled a hole in the front cover to allow an allen wrench to be inserted into the alternator bolt--to turn over the engine. Same hole size as the rubber plug for the timing hole over the flywheel. Note that the hole isn't concentric with the cover casting. I located it by placing a gob of clay over the approximate position on the inside of the cover, and gently pressing it in position.

Having the "inspection" hole in the cover makes it unnecessary to disconnect the ground wire or remove the cover. Just pull the spark plugs, shift into neutral, insert the allen wrench, and you're ready.

After pulling the valve covers (in the shop), I usually torque the heads. That just takes a moment, and ensures everything is at optimum for setting the valves. When torquing a head nut, I crack it loose about a quarter turn, then snug it down to spec. I go to the opposite nut across the head, and torque in a cross pattern.

If any rocker arm support blocks show excessive rocker arm clearance, there are shims available. Before BMW came out with rocker shaft shims, I used some spare Moto Guzzi shims. ("thrust washers" if you prefer)

While we're on the subject, let's note that weeping valve cover gaskets are usually a result of the outside of the head warping from heat. You can go through all the trouble of having a machine shop true them up, but in my experience they just warp some more over time.

My fix is to glue the valve cover gasket in place with high temp silicone gasket sealer. I carefully clean the head surface and gasket with brake cleaner, then apply a careful coat of gasket sealer to the gasket, and temporarily install the valve cover with only the center bolt turned hand tight. That allows the cover to squeeze the sealer to an even level. After a few hours, I remove the valve cover and carve away any excess gasket sealer to make sure it doesn't get swallowed into the innards. It helps to apply a coat of grease to the valve cover contact area to keep it from sticking to the gasket.

With care, the sealer will hold the gasket securely in place for several valve adjustments, and will seal those embarrassing oil weeps. BTW, use the "foreign" type to avoid corroding the aluminum.

pmdave

[mmmalmberg]

PMD - The hole in the front cover is clever. But what's the issue with turning by the rear wheel, which is so simple? I never totally loved putting torque on the alternator bolt to turn the engine, depending on how tight the engine is.

Also, I know I must just be lucky, but out of 10 or so airheads, I've only had one with difficulty related to the v.c. gasket, and that was a warped cover on a /2. Thank my lucky stars I guess. The "roll-your-own" silicon gasket sounds like a good solution.

[orbitangel]

I've drilled a hole in the front cover to allow an allen wrench to be inserted into the alternator bolt--to turn over the engine. Same hole size as the rubber plug for the timing hole over the flywheel. Note that the hole isn't concentric with the cover casting. I located it by placing a gob of clay over the approximate position on the inside of the cover, and gently pressing it in position.

Having the "inspection" hole in the cover makes it unnecessary to disconnect the ground wire or remove the cover. Just pull the spark plugs, shift into neutral, insert the allen wrench, and you're ready.

pmdave

I think that is a hell of a good idea! I should have thought of that!

Shoot - BMW should have thought of it!

Please take a bow. :bow

[pmdave]

I've also used the rear wheel to turn the engine, selecting second or third gear. But turning the wheel is relatively crude. The engine can jerk as the drive spring suddenly overcomes friction, or the splines take up the slack.

I don't believe it's absolutely critical to adjust valves at TDC. The cams are ground smoothly enough that a few degrees off TDC won't make much difference. But given a choice, I'd prefer to get the engine quickly to TDC, and that's a lot easier by turning the engine without the drive/shaft/gearbox in the equation. With the plugs removed, the rotor bolt should be tough enough to roll the motor over. And if the bolt is so weak it snaps, I'd rather find that out in the shop than out on the road somewhere in the pouring rain.

We don't have to do this in lockstep, y'know.

pmdave:dance

[mmmalmberg]

PMD I absolutely agree, to each his own. Just wanted to know as it's the second mention I'd heard of not using the rear wheel. I use 5th gear and it works great for me. If I were an alternator-bolt-turner, I'd be right there with you with the hole in the front cover!

[20774]

I used to use the alternator rotor bolt to turn the engine. When I was green behind the ears, I left the plugs in and noted how difficult that was. Then I started removing the plugs. But I don't like removing the plugs when it's not really necessary. I guess I have some kind of irrational fear of those aluminum threads and the steel spark plug not playing nice! So, now I just put the tranny in 5th gear, turn the rear wheel while watching the valve motion, then stop when the intake valve starts to head to being closed. I sit beside the bike and lightly bump the rear wheel the few more degrees until I see TDC.

[dduelin]

I found that I had warped covers and heads - the worst gap was .011 between cover and head! My solution was the take the covers to a machine shop and have them trued then I used the tiniest uniform bead of RTV gasket sealer on the valve cover I could apply. I used a silicone gasket with the RTV sealant only on the valve cover side as I said. I held the cover in place with the bolt and nut turned only one turn down so the sealant was not squeezed out and it filled the gap spots on the head side by pressing the gasket against the warped head side non-conformaties. I left if overnight to set up then tightened the covers down. The silicone gasket conforms to the warps in the heads and no leaks, weeps, or seeps for a couple thousand miles now.